An articulated machine, such as a motor grader, is a versatile apparatus for road work, ditch work, site preparation and other surface contouring and finishing tasks. The versatility of a motor grader is provided in large part by its multiple course setting and course change options. In particular, a motor grader typically includes a steering function implemented via steerable ground engaging wheels while also allowing some degree of course correction or steering via lateral arching or articulation of the machine frame. In this manner, for example, a motor grader may be steered and articulated to follow a curve without driving the rear wheels across the area inside the curve and disturbing the just graded area.
As should be recognized from the above, motor graders, and other articulated machines, are complex pieces of heavy machinery and are operatively complex. Controlling a motor grader includes numerous hand-operated controls to steer the front wheels, position the blade, control articulation, control auxiliary devices such as rippers and plows, and various displays for monitoring machine conditions and/or functions. Control of a motor grader requires highly skilled and focused operators to position the blade while controlling steering.
In order to track front wheels to back wheels, some systems may limit steering angle to the maximum corresponding articulation angle. For example, U.S. Pat. No. 8,548,680 tracks articulation angle to steering angle up to the maximum articulation angle and then limits further changes to steering angle.
However, there may be cases when an operator would like additional control of the articulation angle that does not necessarily involve having the rear wheels follow in the front wheel tracks.